Best Practices for Citrix XenDesktop with Provisioning Server

Transcription

1 Best Practices - Citrix XenDesktp with Citrix Prvisining Server Cnsulting Slutins Best Practices fr Citrix XenDesktp with Prvisining Server Overview Citrix XenDesktp ffers a next-generatin, user-centric desktp virtualizatin slutin that prvides a cmplete system fr desktp delivery. Fr infrmatin technlgy (IT) rganizatins, XenDesktp greatly simplifies the desktp lifecycle management prcess and drives dwn the cst f desktp wnership by separating the delivery f the desktp perating system frm applicatins and user settings. Citrix XenDesktp, in cncert with Prvisining Server fr Desktps virtual desktp prvisining capabilities, prvides a pwerful slutin that simplifies the delivery f desktps t end users. When designing a Citrix XenDesktp slutin, it is imprtant t take int accunt hw XenDesktp with Prvisining Server will interact with an rganizatin s existing critical infrastructure and services. These cmpnents include: directry services, netwrk and security architecture, server hardware types, strage infrastructure, virtualizatin strategies and desktp perating system types. This whitepaper discusses cnsideratins when designing and implementing Citrix XenDesktp with Prvisining Server in an enterprise envirnment. It is imprtant t nte that this whitepaper is nt a step-by-step guide t deplying XenDesktp architectures, but rather it lks t identify best practices fr prviding the best perfrming, mst stable, and scalable implementatin f XenDesktp with Prvisining Server. Target Audience This dcument has been develped fr infrmatin technlgy (IT) infrastructure specialists wh are respnsible fr planning and designing a Citrix XenDesktp infrastructure fr desktp virtualizatin. These specialists include cnsultants, system architects, and thers wh are cncerned with design decisins related t virtualizatin, specifically the virtualizatin f desktp systems.

2 2 Table f Cntents Overview... 1 Target Audience... 1 Citrix XenDesktp Overview... 3 Citrix Prvisining Server Overview... 3 Best Practices... 4 Netwrking... 4 Strage... 5 XenDesktp Desktp Delivery Cntrller... 7 Prvisining Server... 9 Virtual Desktp Images/Target Devices Scalability Resurces... 18

3 3 Citrix XenDesktp Overview Citrix XenDesktp prvides a cmplete virtual desktp delivery slutin by integrating several cmpnents with advanced cnfiguratin tls that simplify the creatin and real-time management f the virtual desktp infrastructure. The cre cmpnents f XenDesktp discussed in this paper are: Desktp Delivery Cntrller (DDC). Installed as an infrastructure cmpnent n servers, the cntrller authenticates users, manages the assembly f users virtual desktp envirnments, and brkers cnnectins between users and their virtual desktps. Virtual Desktp Agent (VDA). Installed n each virtual desktp, the agent cmmunicates with the DDC and enables a direct ICA (Independent Cmputing Architecture) cnnectin between the virtual desktp and the users endpint device. Desktp Receiver. Installed n users endpint devices, the Desktp Receiver enables direct ICA cnnectins frm endpint devices t virtual desktps. The XenApp plug-in can als be used in place f the Desktp Receiver, but the new features within the ICA tlbar wuld nt be available. Citrix Prvisining Server Overview Prvisining Server s infrastructure is based n sftware-streaming technlgy. Using Prvisining Server, administratrs prepare a device (Master Target Device) t be imaged by installing an perating system and any required sftware n that device. A virtual disk (vdisk) image is then created frm the Master Target Device s hard drive and saved t the netwrk (n Prvisining Server r back-end strage device). Once the vdisk is available frm the netwrk, a target device n lnger needs its lcal hard drive t perate, as it bts directly frm the netwrk. The Prvisining Server streams the cntents f the vdisk t the target device n demand, in real time. The target device behaves as if it is running frm its lcal drive. Unlike thin-client technlgy, prcessing takes place n the target device. The cmpnents f Citrix Prvisining Server discussed in this paper are: Prvisining Server (PVS). A Prvisining Server is any server that has the Stream Service installed. It is used t stream sftware frm vdisks as needed, t target devices. In sme implementatins, vdisks reside directly n the Prvisining Server. In larger implementatins, Prvisining Servers btain the vdisk frm a netwrk strage device. Prvisining Servers als retrieve and prvide cnfiguratin infrmatin t and frm the Prvisining Server database. Prvisining Server architecture includes ptins t ensure high availability and lad-balancing f cnnectins between target devices and their vdisks. vdisk Images. vdisks are disk image files n a Prvisining Server r n a shared strage device. vdisks are cnfigured t be in either Private Image mde, where changes made by the user are kept n the image, r Standard Image mde (read-nly), where changes made by the end user are discarded upn shutdwn. Target Devices. A device, such as a desktp cmputer r server, that bts and gets its perating system and sftware frm a vdisk n the netwrk, is cnsidered a target device. Write Cache Files. When using a standard image mde the vdisk is set t read-nly mde. Each target device then builds a cache that stres any writes that the perating system needs t perfrm such as applicatin streaming, rutine applicatin prcessing tasks r system paging. Several scenaris and ptins fr string the write cache files will be discussed later in this dcument. Netwrk Strage. vdisks are generally stred n netwrk strage devices (SAN, NAS, Windws File Servers, etc.). Leveraging netwrk strage devices allws fr redundancy and high availability f the vdisk images.

4 4 Best Practices This sectin cntains the best practices fr a XenDesktp and Prvisining Server deplyment. These best practices are divided int the fllwing areas: Netwrking Strage XenDesktp Desktp Delivery Cntrller Prvisining Server fr Desktps Virtual Desktp Images/Target Devices Scalability Cautin! This dcument cntains recmmendatins that require using the Registry Editr. Using the Registry Editr incrrectly can cause serius prblems that may require reinstalling the perating system. Citrix cannt guarantee that prblems resulting frm the incrrect use f the Registry Editr can be slved. Use the Registry Editr at yur wn risk. Always back up the registry befre editing any values. Netwrking Dmain Name System. A key infrastructure cmpnent used when registering target devices with the DDC is the existing Dmain Name System (DNS) envirnment. When target VM begin the registratin prcess, the DDC will perfrm a DNS query and try t cmmunicate with the target device using the Fully Qualified Dmain Name (FQDN) f the registering machine. The target devices, which typically btain their IP addresses via DHCP, need t be able t dynamically update their Hst (A) recrds in DNS. It is als recmmended that the DDCs als be able t update their wn DNS recrds shuld additinal DDCs be brught nline, changed mved r added t the envirnment. While standard file-based strage such as a hsts file will prvide prper DNS reslutin in Prf f Cncept (POC) envirnments, Citrix recmmends implementing Active Directry integrated DNS in enterprise deplyments. If the DNS zne is integrated with Active Directry, rganizatins have the benefit f secure dynamic updates, as well as the ability t use Access Cntrl List (ACL) editing features t cntrl which machines can update the DNS system. This allws an rganizatin t specify the cmputers that are allwed t update their DNS recrds (XenDesktp VMs/Prvisining Server target devices and DDCs). Dynamic updates are a key feature f DNS, which allw dmain cmputers t register their name and IP address with the DNS server autmatically when they cme nline r change IP addresses thrugh the DHCP server. This frm f update eliminates the need fr manual entries f names and IP addresses int the DNS database. The security aspect cmes int play when an autmatic update frm a client t the DNS database culd pssibly pen an attack vectr fr a malicius entry. Therefre, secure dynamic updates will verify that the cmputer that is requesting the update t the DNS server als has an entry in the Active Directry database. This means that nly cmputers that have jined the Active Directry dmain can dynamically update the DNS database. Nte: When using Windws based standard zne strage, the DNS Server service is cnfigured t disallw dynamic updates n its znes by default; therefre, dynamic updates must be explicitly allwed fr the zne. It is als imprtant t nte that reverse lkup znes are used when the virtual desktps are added t a desktp grup within the Access Management Cnsle. The IP address f the virtual desktp is mapped t the FQDN using the reverse lkup DNS zne. Prvisining Server. T prvide ptimal thrughput, Citrix recmmends using multiple Netwrk Interface Cards (NIC)s in Prvisining Server machines. One NIC shuld be cnfigured fr PXE cmmunicatin n the netwrk. A teamed pair shuld be cnfigured fr streaming the vdisks via the PVS Stream Service. A secnd teamed pair may be required fr netwrk access t enterprise strage systems r file shares. When pssible, streaming vdisk data shuld be islated frm nrmal prductin netwrk traffic such as Internet brwsing, printing, file sharing, etc. using dedicated netwrks r VLAN s.

5 5 Strage Strage requirements fr Prvisining Server implementatins greatly depend upn the number f vdisk images t be created and maintained, the type f vdisks that will be used (Standard Image Mde vs. Private Image Mde), the perating system installed in the image, what cmpnents r applicatins are installed n each image, plans fr ptential future applicatin installatins, and strage lcatin f the write cache file fr each prvisined wrkstatin. Types f vdisks. When using Standard Mde vdisks, many target devices bt frm the same vdisk. Hwever, space is nly required t stre ne cpy f each vdisk. A secnd cpy shuld be created and be used fr updates t the vdisk. When using Private Mde vdisks, each target device must have its wn cpy f the vdisk, requiring additinal strage space fr each target device. When using a Private Mde disk as the base image fr a Standard Image deplyment, d nt add the vdisk t Active Directry if it will be used as the Standard Image. When a previusly installed Private Mde image bts the vdisk in Standard Image Mde, the Dmain Cntrller will already cntain the unique machine infrmatin (SID) in Active Directry and an errr message will ccur. Instead, let PVS manage the Active Directry machine accunts. vdisk Size Estimates. The size f the vdisk depends greatly n the perating system and number f applicatins t be installed n the vdisk. The vdisk grws larger as mre applicatins are installed in the vdisk. Citrix recmmends creating vdisks larger than are initially necessary t leave rm fr additinal applicatin installs r patches if necessary. Based n past experience, Citrix recmmends rganizatins use the fllwing general sizing estimates when determining the strage requirements. The estimates were made based n an perating system with nly a few applicatins installed such as Micrsft Office. These estimates may nt accurately reflect the required sizes f vdisks in every envirnment; thus, each rganizatin shuld determine the space requirements fr their vdisk images individually. Operating System Windws XP Windws Vista Estimated vdisk Size 15GB 25GB T estimate the size f the vdisk required, fllw these guidelines: Target Device Space. Identify the amunt f space currently in use by the master target device. This can be accmplished by examining the prperties f the disk. A typical installatin f Windws XP with n lcal applicatins added culd cnsume between 1 and 3GB f space n a disk drive. A typical installatin f Windws Vista cnsumes apprximately 6GB f space n a disk drive. Applicatin Sizing. As applicatins are installed, the amunt f space in use increases. If the plan is t add applicatins int the vdisk image after capture, then the vdisk shuld be sized t allw fr the additinal space requirements. Citrix recmmends adding an additinal 25% f space t the initial ftprint f the image, allwing rm fr any additinal applicatin installatins. T minimize the strage space required, Citrix recmmends the fllwing: Minimize Applicatins n Each vdisk. Minimizing the number f installed applicatins helps reduce the ftprint f each vdisk. In additin t reducing the strage capacity, keeping the vdisk as generic as pssible allws an rganizatin t leverage the same vdisk fr many wrklads. Delivering persnalized applicatin sets t the desktp via published applicatins hsted n XenApp servers r applicatin streaming via Citrix Streaming Server further minimizes the applicatins n each vdisk. Minimize the Number f vdisks. Each vdisk requires physical disk space equal t the size f the vdisk. Cnsequently, reducing the number f vdisks reduces the strage space requirements. Citrix recmmends keeping at least ne backup cpy f each vdisk t be used t make updates when required. An rganizatin shuld cnsider allcating 2x the amunt f disk space required fr each vdisk that it plans t maintain. Write Cache File. Each target machine cntains a vlatile write cache file that is deleted upn each rebt cycle. The size f the cache file fr each VM depends n several factrs, including the types f applicatins used, user wrklads, and rebt frequency. A general estimate f the file cache size fr a prvisined wrkstatin running nly text-based

6 6 applicatins such as Micrsft Wrd and Outlk and is rebted daily is abut MB. If wrkstatins are rebted less ften, r graphic intensive applicatins (such as Micrsft PwerPint, Visual Studi, r CAD/CAM type applicatins) are used, cache file sizes can grw much larger. As each envirnment s applicatin wrklad can vary, Citrix recmmends that each rganizatin perfrm a detailed analysis t determine the expected cache file size required fr their envirnment. Cache File Lcatin. There are several ptins fr string the cache file fr prvisined desktps. Cmmn lcatins include; target based physical lcal strage, client disk (virtual machine vdisks), and enterprise strage based (SAN/NAS) disk envirnments. Each f these ptins has benefits and limitatins; thus, it is imprtant t evaluate the specific requirements f the rganizatin befre determining the cache file lcatin. The benefits and limitatins f each ptin are described belw. Physical Lcal Strage. If physical desktps r blade servers are being used, Citrix recmmends leveraging the target device s RAM r hard disk t stre the cache files. When lcating the cache file n a lcal physical strage device, cnsider the fllwing: Since accessing RAM is cnsiderably faster than reading and writing data t a hard disk, placing the cache file in RAM will yield better perfrmance when cmpared t a hard disk. Placing the cache file in RAM will ften prvide the best perfrmance fr a single applicatin envirnment. When RAM is used fr the cache file, the cache file is limited in size by the amunt f physical RAM available in the target machine. If the cache file is expected t grw larger than the amunt f available physical RAM in the device, the device s hard drive shuld be used instead. Shuld the RAM based cache file becme filled, undesired result/errrs may ccur since there is nt enugh space t write the cached data. There is generally mre space available fr the cache file n the hard drive n a target machine than in memry. If the target devices are diskless and d nt cntain hard drives r enugh memry fr the required size f the cache file, then the cache files can be stred n a shared enterprise strage device and prxied via the Prvisining Server fr Desktps. Client Disk (Virtual Machine vdisks). When leveraging a virtual machine infrastructure t hst the desktps, an rganizatin can als leverage enterprise strage assciated with each VM r the VM s allcated RAM fr the write cache lcatin. Fr example, each VM may be created with an additinal 1 GB disk t stre the cache file n each target device s vdisk. When using virtual machine vdisk based cache lcatins, cnsider the fllwing: String the cache file as part f the VM requires additinal RAM r disk space equal t that f the cache file t be allcated in additin t the size required fr each unique VM. If the target cache file is hsted n the PVS server, high availability f the cache file will nt be present. T enable a cache file that is highly available, use the PVS Prxy Mde mdel belw. This mdel generally prvides gd perfrmance, when the PVS server cntains a fiber channel r dedicated Hst Bus Adapter (HBA) card cnnected t a SAN. Shuld fiber channel cards nt be available, Gigabit NICs may be used t cnnect t CIFS based netwrk shares. Citrix recmmends that the PVS server cntain multiple NICs; ne teamed pair dedicated fr streaming and ne teamed pair dedicated fr netwrk traffic t the enterprise strage netwrk (iscsi, CIFS, NAS, etc.) and ne NIC cnfigured fr PXE traffic. This ptin prvides added resiliency in the event f a failure since nly a single VM will be affected if the lcal disk assciated with the VM runs ut f space. Each VM must be able t see the additinal disk that is assciated with the VM fr this ptin. Utilizing a client disk fr the cache file will lwer the verall netwrk traffic when cmpared t the enterprise server based ptin. In additin, a lcal file is required fr full system dump tracing. Enterprise Server Based (PVS Prxy Mde). The cache file can als be stred n a shared enterprise strage slutin (SAN/NAS) accessed via the Prvisining Server. In this case, the Prvisining Server wuld act as a prxy between the virtual machine and the strage slutin. T create High Availability (HA) architectures, a minimum f tw PVS servers are required.

7 7 This slutin allws fr the cnfiguratin f PVS in High Availability (HA) mde. If an HA mde failure ccurs within the PVS infrastructure, any remaining servers can begin servicing the failed requests withut interruptin t the target device. If the vdisk file is als placed n the shared strage lcatin, XenMtin features can als be enabled Prxying the cache traffic thrugh the PVS in this manner impacts the netwrk I/O and reduces the scalability f each PVS server. This will impact the number f active clients that can be supprted by a single PVS architecture.. Prper sizing f the strage lcatin is critical in this scenari. If the shared strage lcatin fills up and n disk space remains fr cache, all virtual machines may experience perfrmance issues. The Write Cache needs t be lcated n shared strage t benefit frm XenServer's HA feature (XenMtin between XenServers) Fr enterprise deplyments using HA cnfiguratins, Citrix des nt recmmend string the cache file lcally n the PVS server. If the cache file is stred lcally n the PVS, each PVS becmes a single pint f failure, and HA cnfiguratins are nt available. Each rganizatin will need t determine their individual Service Level Agreements (SLA) t determine whether an HA cnfiguratin is required fr their unique desktp use cases. When a small SLA windw is required, ne may chse t use bth XenMtin and PVS in HA mde t prvide a cmplete fault tlerant slutin. This wuld require the vdisk and cache file t be lcated n shared strage at the expense f lwering the verall scalability f the PVS server. If a large SLA windw is available, then Citrix recmmends using lcally stred cache files when pssible fr ptimal perfrmance. SAN vs. NAS. In HA scenaris, a shared SAN is required and a LUN must be accessible frm multiple hsts (PVS Servers r targets). Read-nly LUN s can be utilized fr string vdisks in standard mde. Private Image Mde vdisks require read and write access. When HA architectures are required, using a NAS head t allw multiple machines access t the LUN r traditinal NAS architectures with RAID disks shuld be used. Strage ptimizatins such as placing vdisks n LUNs that span separate disk spindles rather than cntiguus blcks will further imprve thrughput. Determining Expected Cache File Size. Citrix recmmends using a pilt/poc envirnment t determine the expected size f the cache files. T determine the file size within the pilt/poc envirnment, cnfigure the write cache t be lcated n the Prvisining Server and have several different types f end-users (graphical applicatin users, text-based task wrkers, etc.) wrk n their prvisined desktps. After several full days f heavy use, the administratrs can lk at the size f each f the cache files n the Prvisining Server. This will give a rugh estimate f hw large the cache files can grw in the prductin envirnment. In the prductin envirnment, gracefully rebting the desktps everyday will help reduce the size f the cache file since the files are purged n each rebt cycle. Rebt Prvisined Wrkstatins Frequently. The write cache file fr prvisined wrkstatins can grw quite large, and will cntinue t grw until the wrkstatin is rebted. Depending upn the applicatins used and the frequency f rebts, the write cache can grw as large enugh t impact an rganizatin s strage slutin. The cache file is cleared ut upn wrkstatin rebt. Subsequently, the mre frequently the wrkstatin is rebted, the less f an impact the cache files will have. Citrix recmmends rebting wrkstatins daily if pssible. If daily rebts are nt pssible, Citrix recmmends rebting wrkstatins at least nce per week t reduce the strage impact f cache files. Nte: A graceful shutdwn r restart is required t clear the cache file. Pwering dwn the machine withut a graceful shutdwn will nt clear ut the cache file. XenDesktp allws cnfiguratin f lgff behavir s this prcess can be autmated as well. XenDesktp Desktp Delivery Cntrller Uninstall Web Interface and IIS. XenDesktp autmatically installs IIS and Web Interface as part f the Desktp Delivery Cntrller (DDC) installatin. Mst rganizatins have existing web server infrastructure that can be leveraged fr Web Interface fr XenDesktp. Nt installing these cmpnents will help increase the perfrmance and scalability f the DDCs in a prductin envirnment. Organizatins can take tw appraches if they have an existing IIS infrastructure: During the install, use the Setup.exe -nsites parameter, which will nt install Web Interface. If the install has already ccurred, an rganizatin shuld cnsider uninstalling this cmpnent r disabling the assciated services.

8 8 Separate the Farm Master and Cntrller. By default, in a XenDesktp farm the initial Desktp Delivery Cntrller (DDC) installed is the farm master with specific duties as the data cllectr, perfrming desktp reslutin peratins during desktp launches, and managing the hsting infrastructure. This single server has the rle f Data Cllectr and Cntrller. When there are multiple servers in a farm, it is ften desirable t separate the functins f Cntrller and Data Cllectr by delegating these functins t different servers. These ther duties can be better perfrmed by ther Desktp Delivery Cntrller machines in the farm, leaving the farm master machine t cncentrate n its wn rle requirements. T separate the rles, the actins t be taken fall int tw parts: ensure that a particular machine is chsen t be the farm master and ensure that unnecessary duties are nt perfrmed by that machine. Each Desktp Delivery Cntrller machine in the farm can ptentially becme the farm master in an electin prcess. This electin prcess can be influenced by settings n the varius server machines, and ne (r mre) machines can be cnfigured s that they are the preferred farm master, while ther machines are cnfigured t nly take n the farm master rle if the preferred machines are unavailable. This preference indicatin is achieved by use f registry entries n the varius server machines. Each machine can be cnfigured t have ne f three settings: Master servers with this setting are preferentially chsen as the farm master. Backup servers with this setting are preferentially chsen as the farm master when the master server is unavailable. Member servers with this setting are nrmally nt the farm master, but can assume the farm master rle when nne f the master r backup servers is available. The desktp launch request is the sle functin f the DDC master and handles the lgic f launching cnnectins. When cnfiguring Web Interface t pint t a DDC member, Web Interface will frward the launch request t the DDC master. If the DDC master server becmes unavailable, an electin ccurs and anther member server will assume the DDC master rle. Once the Desktp Delivery Cntrller has established the cnnectin t the virtual desktp, ICA establishes a direct cnnectin between the virtual desktp and the endpint (client machine). The Delivery Cntrller is n lnger in the line f traffic. As such, the demand n it is diminished and it can scale sufficiently. When using multiple DDCs, Citrix recmmends dedicating a machine as the master cntrller and all ther servers shuld be cnfigured as member servers. Web Interface servers shuld be cnfigured t pint t member servers t minimize the CPU lad placed n the cntrller server during perids f heavy lgn rates. T cnfigure a server these settings, edit the fllwing registry keys and restart the server: HKLM\Sftware\Citrix\IMA\RUNTIME\UseRegistrySetting DWORD=UseRegistrySetting Value=1 HKLM\Sftware\Citrix\IMA\RUNTIME\MasterRanking DWORD=Value Value= 1 indicates Master 2 indicates Backup 3 indicates Member Fr mre infrmatin, please see Citrix Knwledge Base Article CTX Thrttle Cmmands t Virtual Machine Hsting Infrastructure. When sending a high number f pwer n/ff cmmands t the virtual machine hsting infrastructure (VMware Virtual Center, XenCenter, Hyper-V), the hsting infrastructure culd becme verwhelmed and unrespnsive fr a shrt perid f time while all f the requests are queued and prcessed. By default, the cmmunicatin between the pl management service n the DDC and the hsting infrastructure is thrttled t 10% f the ttal pl. Fr example, if there are 500 VMs in the desktp grup, nly 50 VM pwer peratin requests will be sent at a time. When pls grw even larger, (ver 1000 desktps), this culd result in apprximately 100+ pwer n/ff requests being sent cncurrently t the hsting infrastructure. The hsting infrastructure may becme verladed during the fllwing scenaris:

9 9 When the idle pl cunt significantly increases fr a cncurrent peak time There is a small duratin between lgn and lgff events. Fr example, a cmpany emplys a three shift wrking day. A grup f users will lgn in the mrning and lgut when their shift is finished. The next shift f users will begin t lgn at the same time that the previus grup lgs ff resulting in a very small windw where large numbers f users lg n and lgff (5-15 minutes). It may be necessary t thrttle the number f pwer requests sent t the virtual machine infrastructure at a single time. T mdify the number f cncurrent requests, edit the fllwing cnfiguratin n each DDC. This example thrttles the number t 20 cncurrent cmmands. Open C:\Prgram Files\Citrix\VmManagement\CdsPlMgr.exe.cnfig Add the fllwing line in red: <?xml versin="1.0" encding="utf-8"?> <cnfiguratin> <appsettings> <add key="lgtcdf" value ="1"/> <add key="lgfilename" value ="C:\cdslgs\VMManager.lg"/> <add key="lgdebug" value="1"/> <add key= MaximumTransitinRate value= 20 /> </appsettings> </cnfiguratin> Save the file and restart the DDC. The DDC r the Pl Management Service must be restarted fr the new value in the.net cnfiguratin file t be read by the DDC. The value ( MaximumTransitinRate value= 20 ) included in this example shuld nly be cnsidered as a pint f reference when cnfiguring the cncurrent cmmand values. This value will vary based n each envirnment s unique hardware platfrm and use case. Citrix recmmends that each rganizatin prperly test the cnfiguratin befre determining the ptimal balance between the number f cncurrent cmmands that can be serviced and the perfrmance/respnsiveness f the hsting infrastructure when sending pwer cmmands frm the DDC. Prvisining Server Disable Checksum Offlading n Netwrk Adapter. Checksum fflad parameters, which are nt cmpatible with the Prvisining Server netwrk stack, may cause slw perfrmance when enabled n the physical netwrk adapter. Symptms f slw perfrmance can include: Excessive amunt f retries Slw ICA perfrmance within virtual machines Freezing r lcking while using Windws XP Service Pack 2 virtual machines vdisk retries during nrmal peratin when a Windws XP Service Pack 2 virtual machine is already nline and in waiting mde Slw hsted applicatin launch when using Presentatin Server 4.5 and publishing applicatins in XenDesktp Citrix recmmends disabling Checksum Offlad n the netwrk adapter f bth the Prvisining Server as well as the target devices. On many NICs, checksum fflading can be disabled by pening the Netwrk Interface Card (NIC) prperties and selecting the advanced cnfiguratin tab. Sme NICs d nt ffer this setting in the prperties page (i.e. target devices running n virtual machines). T change the Checksum Offlad parameter value, create and edit the fllwing registry key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentCntrlSet\Services\Tcpip\Parameters DWORD = DisableTaskOfflad

10 10 Value = 1 Nte: The registry value described abve may nt exist by default n sme systems and may need t be created fr this value t be applied prperly. Fr mre infrmatin, please see Micrsft Knwledge Base Article Disable TCP Large Send Offlad. The TCP Large Send Offlad ptin allws the TCP layer t build a TCP message up t 64 KB lng and send it in ne call via IP and the Ethernet device driver. The adapter then re-segments the message int multiple TCP frames fr wire transmissin. The TCP packets sent n the wire are either 1500 byte frames fr a Maximum Transmissin Unit (MTU) f 1500 r up t 9000 byte frames fr a MTU f 9000 (jumb frames). Re-segmenting and queuing packets t send in large frames can cause latency and timeuts t the Prvisining Server and therefre this shuld be disabled n all Prvisining Servers and target devices. T disable the Large Send Offlad values, pen the Netwrk Interface Card (NIC) prperties and select the advanced cnfiguratin tab. Sme NICs d nt ffer this setting in the prperties page (i.e. target devices running n virtual machines). T disable the Large Send Offlad parameter value, create and edit the fllwing registry key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentCntrlSet\Services\BNNS\Parameters\ DWORD = EnableOfflad Value 0 Fr mre infrmatin, please see Citrix Knwledge Base Article CTX Aut Negtiatin. Aut Negtiatin can cause lng bting times and PXE timeuts, especially when bting multiple target devices. Citrix recmmends hard-cding all Prvisining Server prts (server and client) n the NIC and n the switch prt t disable the aut negtiatin feature cnfigure the cnnectin speed. Disable Spanning Tree r Enable PrtFast. With Spanning Tree Prtcl (STP) r Rapid Spanning Tree Prtcl, the prts are placed int a "blcked" state while the switch transmits Bridged Prtcl Data Units (BPDU) and listens t ensure that the BPDUs are nt in a lpback cnfiguratin. The amunt f time it takes fr this prcess t cnverge depends n the size f the switched netwrk that might allw the Prebt Executin Envirnment (PXE) t time ut causing the VM t enter a wait state r rebt until the cnditin is cleared and the PXE prcess can resume. T reslve this issue, disable STP n edge prts cnnected t clients r enable PrtFast r Fast Link depending n the managed switch brand. Refer t the table belw: Switch Manufacturer Cisc Dell Fundry 3COM Fast Link Optin Name PrtFast r STP Fast Link Spanning Tree FastLink Fast Prt Fast Start Maximize the System Cache. All traffic that ccurs between the vdisk and the target device passes thrugh the PVS machine regardless f where the vdisk resides. Using Windws Server 2003 file caching features can imprve vdisk deplyment efficiency. The perating system caches the file reads and write data peratins at the blck level. When a single target device is bted frm a shared vdisk, subsequent clients will nt require disk read I/O t perfrm similar peratins. The OS caching mechanism will nly cache the blcks that were accessed, nt the entire vdisk file. The file read data will stay in the cache until it is flushed t make space fr newer data. T increase the speed at which the vdisk is streamed, the Prvisining Server shuld be ptimized fr file caching such that the file cache is cntained in server RAM rather than increasing disk I/O by reading the files frm the server s hard disk. The system cache can be maximized n the Prvisining Server by fllwing these steps: Right-click My Cmputer and select the Advanced tab.

11 11 Click the Settings buttn in the Perfrmance sectin f the Advanced tab. Click the Advanced tab f the Perfrmance Optins windw. Ensure System Cache is selected under the Memry Usage sectin. Alternatively, the system cache value can be cnfigured thrugh the registry by using the fllwing key: KEY_LOCAL_MACHINE\SYSTEM\CurrentCntrlSet\Cntrl\Sessin Manager\MemryManagement DWORD=LargeSystemCache Value=1 Fr mre infrmatin, please see Micrsft Knwledge Base Article Team NICs fr Increased Thrughput. Netwrk I/O n the Prvisining Server can be a limiting factr in the scalability f the server. Teaming tw NICs fr thrughput prvides the server with a maximum f 2Gb f netwrk I/O, increasing the netwrk perfrmance helping t alleviate this ptential bttleneck. In additin, teaming the NICs eliminates a single pint f failure if nly ne NIC is enabled. Islate Streaming Traffic. When pssible, vdisk streaming traffic shuld be islated frm nrmal prductin netwrk traffic such as Internet brwsing, printing, file sharing, etc. In this scenari it is best t use multiple NICs; ne fr PXE and teamed NICs fr streaming the vdisks t target machines. Make a Cpy f Each vdisk. In rder t mdify images created with Prvisining Server, it is recmmended that an rganizatin saves a cpy f each vdisk and places it in Private Image mde. By keeping a cpy f the vdisk in Private Mde, the administratr can mdify the vdisk t include any required updates withut affecting the prductin image. Once all required mdificatins have been made, the administratr can use the Prvisining Server Cnsle t cnfigure the target devices t bt frm the newly created vdisk image. Backing up each vdisk is als recmmended fr disaster recvery and business cntinuity purpses. Virtual Desktp Images/Target Devices A clean virtual disk image is critical t the successful delivery f the vdisk t the target device when using Prvisining Server. When develping this vdisk image, it is imprtant t ensure that the master target disk des nt cntain any unwanted infrmatin, such as unused applicatins r user prfiles. The rder in which the master target disk is prepared is als imprtant t ensure the image is clean and NICs are bnded crrectly. Recmmended Desktp Operating System Mdificatins Increase Service Timeuts. When rebting a large number f virtual machines within a shrt perid f time (5-15 minutes, such as during a shift change), it may be necessary t increase the Service Cntrl Manager timeut value t allw enugh time fr the critical XenDektp services t start and register successfully with the available DDCs. Stress testing cnducted by Citrix Cnsulting has shwn that increasing this value t 3 minutes n all virtual target devices may be necessary t allw ample time fr the critical services t start. This timeut can be increased by mdifying the vdisk image with the fllwing registry key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentCntrlSet\Cntrl DWORD=ServicesPipeTimeut Decimal Value= (3 Minutes) Fr mre infrmatin, please see Disable the Windws XP Tur Prmpt fr New Users. By default, Windws XP ntifies all new users that an XP tur can be taken. While this is a nice feature fr new Windws XP users, it typically is annying fr existing users. T suppress the Windws XP tur prmpt fr all new users, fllw these steps edit the fllwing registry key: HKEY_LOCAL_MACHINE\Sftware\Micrsft\Windws\CurrentVersin\Applets\Tur DWORD=RunCunt

12 12 Value=0 Fr mre infrmatin, please see Disable Last Access Time Stamp. Whenever Windws XP reads a file, it stamps the file with the date and time that it was accessed. This feature impacts perfrmance and is generally nt required fr nrmal use, especially when using Standard Image mde. Putting a timestamp n the file that has just been read requires that a write is made t disk, s every time a read is executed, a crrespnding write is als executed. With Prvisining Server, these writes g t the vdisk cache file, which subsequently increases the netwrk traffic if the cache file is stred n the PVS server. Use the u fsutil.exe t disable the last access timestamp behavir. Execute the fllwing cmmand detailed belw and rebt the wrkstatin: FSUTIL behavir set disablelastaccess 1 Turn ff System Restre. System Restre is the feature that allws a cmputer system t be rlled back, r restred, t a pint befre certain events tk place, fr example, prir t specific sftware r hardware installatins. When using a Standard Image mde (read-nly) vdisk, system restre pints shuld be disabled. This can be accmplished by using the PVS Optimizer tl. In additin, the system restre feature can de disabled by cmpleting the fllwing steps: Right-click My Cmputer and then click Prperties. On the Perfrmance tab, click File System. On the Trubleshting tab, select Disable System Restre. Restart the cmputer. Fr mre infrmatin, please see Disable Windws Indexing Service. Windws Indexing Service adds verhead t the PVS vdisk by reading the files frm the vdisk fr indexing. The Windws Indexing Service can be disabled using ne f the fllwing three methds: Use the PVS Optimizer tl and leave the Disable Indexing Services setting enabled. T turn ff indexing fr a specific drive: Right click and Select Prperties. Under the General tab, disable the "Allw the Indexing Service t index this disk fr fast file searching" setting. T disable the indexing service at the service level: Click Start, Run, type services.msc. Change the "Indexing Service" Startup type t Manual r Disable and Apply. Verify that the Indexing Service has stpped. Zer ut Deleted Files. SDelete is a secure file delete utility that can be used t free and cleanup unused space n the image. In shrt, it zeres ut any files that have been freed up by the perating system and helps the image run faster. Fr mre infrmatin abut hw it wrks r where t dwnlad it, visit Usage: sdelete [-p passes] [-s] [-q] <file r directry> sdelete [-p passes] [-z -c] [drive letter] -c Zer free space (gd fr virtual disk ptimizatin) -p passes Specifies number f verwrite passes -s Recurse subdirectries -q Dn t print errrs (quiet) -z Cleanse free space. Citrix recmmends cleaning and zering the free space by using the fllwing cmmand: sdelete c z.

13 13 XenDesktp User Prfiles Special cnsideratin shuld be taken when designing prfiles fr a XenDesktp envirnment as users existing prfile settings will apply t bth XenDesktp VM s and traditinal desktps. When a user has an existing raming prfile and assciated Grup Plicy Objects (GPOs) cnfigured fr their traditinal desktp envirnment, these settings will be applied t the XenDesktp VM upn lgn. These pre-existing settings may nt cntain the prper ptimizatins that benefit the XenDesktp envirnment and may cause undesired perfrmance degradatin and incnsistent results within bth platfrms. Befre migrating users t the XenDesktp platfrm, Citrix recmmends carefully designing a prfile strategy that meets the needs f each unique envirnment. When pssible, Citrix recmmends using raming prfiles with flder redirectin and leveraging Windws 2008 preferences with Grup Plicy client-side extensins (CSEs) fr Windws XP and Windws Vista r using the Citrix User Prfile Manager. Additinal infrmatin abut using CSEs can fund in the fllwing Micrsft Knwledgebase Article: Settings fr the Default User Prfile Users that d nt have a pre-existing.dat files in their prfile r d nt have a prfile strategy can benefit frm settings cnfigured within the default user prfile f the XenDesktp VM. This sectin details settings that will imprve the user experience but are cntained at the user prfile level. T mdify the default user prfile, Citrix recmmends creating a generic user with the apprpriate settings and replacing the default user prfile cntents with the generic user prfile settings. The steps t accmplish this are fund at the end f this sectin. Remve Unnecessary Visual Effects. Visual effects such as menu animatins and shadw effects can slw dwn the respnse time f the desktp. Citrix recmmends disabling any unnecessary visual effects. This can be dne by selecting the Adjust fr best perfrmance setting in the advanced prperties f My Cmputer. T keep the Windws XP Visual Style, scrll t the bttm and check the last bx titled Use visual styles n windws and buttns. Disable the Windws XP Tur Prmpt. If the Windws XP Tur Prmpt was nt turned ff befre lgging in as the base user fr the default prfile, this can be manually disabled n a per-user basis. T disable the Windws XP Tur Prmpt change the fllwing registry key: HKEY_CURRENT_USER\Sftware\Micrsft\Windws\CurrentVersin\Applets\Tur DWORD=RunCunt Value=0 Fr mre infrmatin, please see Frce Offscreen Cmpsitin fr Internet Explrer. Turning this setting ff remves any f the flickering that may display when using Internet Explrer thrugh XenDesktp, by telling Internet Explrer t render the page cmpletely prir t displaying it. This is especially helpful n Internet Explrer 7. Open Internet Explrer. Select Tls > Internet Optins > Advanced frm the menu. Enable Frce ffscreen cmpsiting even under Terminal Services. and restart Internet Explrer. Fr mre infrmatin, please see Remve the Menu Shw Delay. The Start menu has a built-in delay f 400 millisecnds. T increase the menu respnse time, cnfigure the fllwing registry key:fllw these steps t set the delay t 100: HKEY_CURRENT_USER\Cntrl Panel\Desktp REG_SZ=MenuShwDelay Value=100 Disable the Desktp Cleanup Wizard. It is unnecessary t run the desktp cleanup wizard when using Standard Image mde since the desktp is refreshed at each rebt. T stp the wizard frm autmatically running every 60 days disable the Run Desktp Cleanup Wizard every 60 days setting within the Display Prperties > Desktp > Custmize > Desktp Items dialg bx. Fr mre infrmatin please see

14 14 Disable Autmatic Searching f Netwrk Printers and Shares. Autmatic search peridically plls yur netwrk t check fr new shared resurces and adds relevant icns int My Netwrk Places if anything is fund. T prevent Windws XP frm regularly searching yur netwrk disable the Autmatically Search fr Netwrk Flders and Printers setting within Cntrl Panel > Flder Optins; if using the Cntrl Panel Categry View, Flder Optins appears under Appearance and Themes. Turn ff Autmatic Updates. When running in Standard Image mde, using autmatic updates will cause the perating system t dwnlad the same updates each time the image is bted. Citrix recmmends turning ff this feature t avid dwnlading the same updates since the vdisk image cnfigured as read-nly. Three ptins can be used t disable the service: Use the PVS Optimizer tl and leave the Disable autmatic update service bx checked. In the Services Cntrl Panel, change the Startup Type f the Autmatic Updates service t Disabled. Run GPEDIT.MSC and navigate t: Lcal Cmputer Plicy > Cmputer Cnfiguratin > Administrative Templates > Windws Cmpnents > Windws Update. Set the Cnfigure Autmatic Updates t Disabled. Cpy the Base User Prfile the Default User Prfile. After cmpleting all the User Prfile Settings using a generic user, the prfile must be cpied t becme the default user prfile. This can be dne using the prcess belw. Nte: Befre cpying the prfile, be sure t remve any user r machine specific data fr the ICA Client, Passwrd Manager, and EdgeSight. Delete the ICAClient and Passwrd Manager data in the base user s Applicatin Data\Citrix flder and the assciated HKey Current User (HKCU) registry keys. D nt start the EdgeSight agent befre the image is taken. Lgin as an administratr (Lcal Administratr is recmmended) nt as the base user used t make the changes fr the prfile because yu cannt cpy a prfile that is in use. Right-click n My Cmputer > Prperties > Advanced > Settings In the User Prfiles sectin, select the base user prfile that was used t make the changes abve and click Cpy T and brwse t C:\Dcuments and Settings\Default User. Save the path lcatin and change the wner and rights assignment t: Everyne and Permitted t use and cnfirm verwriting the prfile. Preparing a vdisk Image Citrix recmmends the fllwing checklist t prepare the master vdisk image. Nte: Except where specifically stated, when preparing the master target image, all actins shuld be perfrmed while lgged int the master target device as a lcal (nn-dmain accunt) administratr. Als, nte that the rder is slightly different fr sme tasks when creating a Windws XP and Vista image. Fllw the steps described belw fr the apprpriate perating system where specified. 1. Prepare the Hardware. Update the BIOS f the master target device, if needed. Open Device Manager and reslve any unknwn drivers. Ensure that Windws has n issues with the disk and netwrk devices and reslve r delete any devices that appear t be unknwn. Jin the machine t the Active Directry dmain and identify any netwrk cnfiguratins that are incrrect (i.e., TCP settings, DHCP, DNS, WINS, r Time surces). Verify disk is clean and functining prperly. Run CHKDSK /F t verify the integrity f the disk drive. 2. Remve Unused Features and Files. Remve any files in the temprary directries that are nt needed. Use the perating system s disk cleanup utility r third-party prducts that remve unwanted files and settings. Verify the cntents f the C:\TEMP and C:\Windws\Temp directry structure t identify files that can be remved prir t image capture.

15 15 Lcal user prfiles will be captured in the master image if they are n the disk during the image capture. Remve any user prfiles that are nt needed. Remve any applicatins that are nt needed by using the Cntrl Panel. Step thrugh the C:\Prgram Files\ directry structure t identify any applicatins that shuld be remved. Remve any base Windws applicatins r features t cnserve space in the vdisk. Remve any data files and persnal settings that are nt needed. Remve any plicy bjects that are nt needed. Review the lcal settings and plicies t identify plicies that can be remved prir t image capture. 3. Desktp Operating System Optimizatins. Cnfigure the system page file. The page file size shuld be determined based n the amunt f memry allcated t each machine and bserved page file use in the current envirnment. This is generally between MB. The initial and maximum file size shuld be the same. Review the Windws Registry settings t identify settings that may n lnger be needed. Use the Registry Editr (Regedit) r ther third-party tls t cleanup registry settings prir t capturing the image. Fr Windws XP wrkstatins: Install the paravirtualizatin tls (XenServer Tls r VMware Tls.) and rebt the target wrkstatin. Install any lcal running sftware t be included in the image. Citrix recmmends minimizing the number f applicatins installed n the base image. Keeping the number f installed applicatins t a minimum will reduce cmplexity with the image and reduce the verall number f images that need t be maintained. Lg in t the desktp using a dmain accunt with lcal administrative privileges and install and rebt the wrkstatin. Fr Windws Vista wrkstatins: Lg in t the desktp using a dmain accunt with lcal administrative privileges and install the Citrix Virtual Desktp Agent (VDA) and rebt the wrkstatin. Install paravirtualizatin tls (XenServer Tls, VMware Tls, etc.) and rebt the wrkstatin. Nte: The paravirtualizatin tls shuld be installed after the XDA is installed t avid errrs when the XDA executes its startup rutine. This applies nly when using Windws Vista as the target machine s perating system. Install any lcal running sftware t be included in the image. Citrix recmmends minimizing the number f applicatins installed n the base image. Keeping the number f installed applicatins t a minimum will reduce cmplexity with the image and reduce the verall number f images that need t be maintained. 4. Test Cnnectivity: Test cnnectin t VDA using Web Interface and verify that the desktp can be accessed. Disabling the Windws Firewall may be necessary fr cmmunicatin with the XenDesktp Desktp Delivery Cntrller. If the firewall cannt be disabled due t security requirements, ensure exceptins are made s the DDCs can cntact the VMs. Verify cnnectivity thrugh prxy cnnectins. If a prxy server is used in the envirnment, the prxy server may need t be cnfigured t allw traffic frm the client machine t the VDA. 5. Install ICA Clients.

16 16 When XenApp hsted applicatins will be accessed frm the desktp, install the Citrix XenApp Plugin (Prgram Neighbrhd Agent) and cnfigure it t cmmunicate with the XenApp Services (Prgram Neighbrhd Agent Services) site. If Applicatin Streaming will be used, install the Citrix XenApp Plugin fr Streamed Apps (Citrix Streaming Client) then rebt the wrkstatin. Cnfigure all streamed applicatins t pre-cache and run. This will imprve netwrk perfrmance by nt having t stream all f the applicatins t each prvisined wrkstatin upn first use. 6. Optimize PVS. Disable TCP checksum and Large Send Offlad as described here. Retest VDA cnnectin. Verify the Dmain\XenDesktp grup (Cntrllers) has Access this cmputer frm the netwrk privileges. This is cnfigured n the wrkstatin thrugh Lcal Security Plicy > User Rights Assignment. 7. Prepare the Target Machine. Defragment the disk drive. Install PVS target device sftware, then rebt the wrkstatin. Flush the DNS cache using ipcnfig /flushdns n the wrkstatin. Optimize then build image using PVS Optimizer. Shutdwn the wrkstatin (d nt rebt), then exprt the vdisk as a backup. Switch the PVS image t Standard Image Mde. If this machine will be used as a template (i.e. ne has nt been created fr the XenDesktp Setup Wizard) make sure t delete the lcal strage n the Template befre running the Setup Tl. Cnvert the machine t a Template in XenServer, VMware, r Hyper-V. Add a 1MB lcal disk t the template if using VMware r plan t use XenMtin with XenServer 4.1 r earlier. When using VMware, the SCSI driver required fr Prvisining Server is nt installed if there is n lcal disk attached. XenServer 4.1 XenMtin requires a file n the strage repsitry, which is nt the case fr a diskless VM (even thugh memry is transferred between XenServer hsts). Use XenServer 5.0 fr XenMtin fr diskless VMs. If yur target devices bth belng t an Active Directry dmain and are sharing a vdisk, cmplete the fllwing additinal steps: Enable Passwrd Management: In the Prvisining Server cnsle, right click the vdisk yu want t share amng the dmain member target devices. Select Prperties > Optins and select the Enable Active Directry Machine Accunt Passwrd Management check bx. Optinally, enable autmatic passwrd re-negtiatin and set the maximum machine accunt passwrd age n the Service Preferences/Active Directry tab.

17 17 Scalability When cnsidering XenDesktp scalability, it is imprtant t examine the scalability f the cnstituent parts f XenDesktp rather than just viewing XenDesktp scalability in a generalized fashin. Scalability is bserved fr the Desktp Delivery Cntrller, fr Prvisining Server, and fr the virtual machine infrastructure. This sectin will discuss the factrs that impact scalability fr the Desktp Delivery Cntrller and Prvisining Server. Desktp Delivery Cntrller The heaviest tll n the Desktp Delivery Cntrller ccurs during peak cnnectin times such as when users simultaneusly lgn in the mrning r during shift changes. Mst f the lgn lad n the server is caused by IMA, the Desktp Delivery Cntrller and the Pl management services. Upn cnnectin cmpletin, the ICA prtcl cnnects the endpint and the virtual desktp the Delivery Cntrller is engaged nly t receive heartbeat ntificatins frm the virtual desktps. These desktp ntificatins are far less taxing than the activity at times f peak lgn. When cnsidering large deplyments, it is imprtant t nte that there are several services that nly run n the Delivery Cntrller Zne Master and that all cnnectin requests frm end users g thrugh the Zne Master. As a result, the master cannt be scaled ut by adding servers. It can nly be scaled up by upgrading t a mre rbust server (mre prcessing pwer). Hwever, a XenDesktp farm can be scaled ut fr failver by adding new Delivery Cntrllers, which handle the XDA keep-alives and registratin with the virtual desktps. The Zne Master can becme a bttleneck when desktp grups grw large. As such, Citrix recmmends limiting the number f desktps per grup t The mst cmmn factr that limits scalability f a single Delivery Cntrller is prcessing pwer. In rder t maximize the number f simultaneus cnnectins a single DDC can handle, Citrix recmmends that rganizatins dedicate servers with the maximum prcessing pwer (dual scket r higher with quad cre prcessrs) t serve as the Zne Masters in a XenDesktp envirnment. Prvisining Server The number f target devices that can be supprted per Prvisining Server depends upn the size f the vdisk, strage slutin fr the vdisk placement, lcatin f the write cache file, and wrkflw f end users. The mst cmmn bttlenecks that affect scalability f Prvisining Server are netwrk I/O f the Prvisining Server, disk I/O f the vdisk strage lcatin, and cache file lcatin. The Prvisining Server Streaming Service manages traffic (i.e. a prxy). If the vdisk is lcated n a share, then the Prvisining Server will retrieve the image and distribute it t the target devices (virtual desktps). Therefre as the number f target devices increases per Prvisining Server, the Prvisining Server s NIC will heavily utilized and becme saturated at peak intervals. Teaming multiple NICs can help increase the number f target devices that can be supprted befre the NIC becmes a bttleneck. Disk I/O f the strage slutin can becme a bttleneck as well, as the Prvisining Server (r multiple Prvisining Servers) will be reading frm the disk t btain the vdisk and cache files. The faster the netwrk strage slutin (SAN, NAS, Windws DFS, etc.) can utput the data frm the hard disk, the better the perfrmance f the Prvisining Server will be, and thus increase the number f devices that a single Prvisining Server can supprt withut reducing perfrmance. Additinally, scalability and thrughput can be impacted by the lcatin f the vdisks and cache files within the backend strage system. When string files n the same strage system, Citrix recmmends placing the vdisks and write cache files n separate dedicated LUNs t decrease (and distribute) disk spindle lads and increase vdisk and cache file access speeds. As discussed earlier in this paper, lcating the write-cache n the Prvisining Server reduces the scalability f each Prvisining Server by increasing the prcessr, netwrk I/O, and disk I/O requirements f the Prvisining Server. Citrix recmmends each rganizatin perfrm scalability testing specific t their envirnment based n the existing infrastructure and use cases t determine the number f target devices that can be supprted by a single Prvisining Server. Additinal Prvisining Servers can be added t the architecture t distribute the lad, as well as t prvide redundancy and high availability (HA). Citrix recmmends implementing additinal Prvisining Servers as part f an rganizatin s HA and disaster recvery plans. Recmmended Scalability by Architecture Cmpnent

18 18 The fllwing chart cntains recmmended maximum values fr each cmpnent within the XenDesktp architecture. These values are based n a reference architecture 1 using XenDesktp with XenApp published applicatins. Cmpnent Desktps Per XenDesktp Farm Tested Lgn rate 2 Recmmended Maximums cnnectins ver a five minute perid vdisks per XenServer 30 XenServers 3 in a Pl Up t 28 Prvisining Server fr Desktps (PVS) 500 VM s per machine when using lcal cache files 4. 1 The fllwing represents the critical items t nte abut the testing architecture: XenServer: 8 cres, 64GB RAM server running XenServer 5 Desktp Delivery Cntrller: 2 cres, 8GB RAM running XenDesktp 2.1 Prvisining Server: 2 cres, 8GB RAM running Prvisining Server 5 Desktp Operating System Cnfiguratin Windws XP: Service Pack 3, 1 prcessr, 512MB RAM Windws Vista: Service Pack 1, 1 prcessr, 1GB RAM 2 A 1500 cnnectin limit has been verified ver a five minute duratin, 50 simultaneus cnnectins ccurred per lgn instance 3 XenServer 5.0 was used t determine this value. 4 Lcal cache files were used when determining this value. Using ther cache file lcatins will decrease the scalability f Prvisining Server Resurces Fr further infrmatin n the tpics discussed thrughut this whitepaper please refer t the resurces listed belw: Getting Started with Citrix XenDesktp 2.1 (CTX118041) Desktp Delivery Cntrller 2.0 Administratr's Guide (CTX116843) Citrix Prvisining Server Administratr s Guide (CTX117916) Citrix Prvisining Server 5.0 Installatin and Cnfiguratin Guide (CTX117917) Best Practices fr Cnfiguring Prvisining Server n a Netwrk (CTX ) Prvisining Server 5.0 Techntes XenDesktp 2.0 Techntes

19 19 Ntice The infrmatin in this publicatin is subject t change withut ntice. THIS PUBLICATION IS PROVIDED AS IS WITHOUT WARRANTIES OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING ANY WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON- INFRINGEMENT. CITRIX SYSTEMS, INC. ( CITRIX ), SHALL NOT BE LIABLE FOR TECHNICAL OR EDITORIAL ERRORS OR OMISSIONS CONTAINED HEREIN, NOR FOR DIRECT, INCIDENTAL, CONSEQUENTIAL OR ANY OTHER DAMAGES RESULTING FROM THE FURNISHING, PERFORMANCE, OR USE OF THIS PUBLICATION, EVEN IF CITRIX HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES IN ADVANCE. This publicatin cntains infrmatin prtected by cpyright. Except fr internal distributin, n part f this publicatin may be phtcpied r reprduced in any frm withut prir written cnsent frm Citrix. The exclusive warranty fr Citrix prducts, if any, is stated in the prduct dcumentatin accmpanying such prducts. Citrix des nt warrant prducts ther than its wn. Prduct names mentined herein may be trademarks and/r registered trademarks f their respective cmpanies. Cpyright 2008 Citrix Systems, Inc., 851 West Cypress Creek Rad, Ft. Lauderdale, Flrida U.S.A. All rights reserved. Versin Histry Authr Versin Change Lg Date Jay Leblang 0.1 Original Cntent 10/2/2008 Nick Rintalan 0.2 Technical Review 10/8/2008 Jay Leblang 0.3 Additinal Cntent prvided by Paul Wilsn 10/24/2008 Nick Rintalan 0.4 Additinal Cntent and Revisins 10/28/2008 Duglas Demskis 0.5 Technical Cntent, Technical QA and Revisins 11/25/2008 Chris Straight 0.6 Technical Review 11/26/2008 Duglas Demskis 0.7 Final Revisins and Technical Review 11/26/ West Cypress Creek Rad Frt Lauderdale, FL Cpyright 2008 Citrix Systems, Inc. All rights reserved. Citrix, the Citrix lg, Citrix ICA, Citrix MetaFrame, and ther Citrix prduct names are trademarks f Citrix Systems, Inc. All ther prduct names, cmpany names, marks, lgs, and symbls are trademarks f their respective wners.